Two-stage three-channel Kondo physics for an FePc molecule on the Au(1 1 1) surface

Abstract

We study an impurity Anderson model to describe an iron phthalocyanine (FePc) molecule on Au(1 1 1), motivated by previous results of scanning tunneling spectroscopy (STS) and theoretical studies. The model hybridizes a spin doublet consisting in one hole at the [Formula: see text] orbital of iron and two degenerate doublets corresponding to one hole either in the 3d or in the 3d orbital (called π orbitals) with two degenerate Hund-rule triplets with one hole in the 3d orbital and another one in a π orbital. We solve the model using a slave-boson mean-field approximation (SBMFA). For reasonable parameters we can describe very well the observed STS spectrum between sample bias -60 mV to 20 mV. For these parameters the Kondo effect takes place in two stages, with different energy scales [Formula: see text] corresponding to the Kondo temperatures related with the hopping of the z and π orbitals respectively. There is a strong interference between the different channels and the Kondo temperatures, particularly the lowest one is strongly reduced compared with the value in the absence of the competing channel.

Heat current across a capacitively coupled double quantum dot

“…Some examples are present in nanoscopic systems. 16,17,[49][50][51][52][53][54][55][56] Evidence of the orbital Kondo effect has also been observed in magnetic systems in which the spin degeneracy is broken. [57][58][59] In our case for the 2-dot model when the on-site energy at both dots is the same, the occupancy of one dot or the other places the role of the orbital degree of freedom.…”

Low-energy physics for an iron phthalocyanine molecule on Au(111)

“…Both configurations are mixed via hybridization with the conduction bands. The model is an extension to finite S of that considered previously by Fernández et al 24 The Hamiltonian is…”

“…They are coupled forming a spin S = 1 by the Hund rules. If this configuration is hybridized with the different excited configurations with one hole, one has a 3-channel Anderson model, which has been studied by Fernández et al 24 using a slave-boson mean-field approximation (SBMFA). In the limit of small hybridization compared with the difference between the energies of both configurations, the model is equivalent to a 3channel S = 1 Kondo model, which is more involved than the 2-channel Kondo model used to describe the system as a non-Landau Fermi liquid 21 .…”

Many-Body Effects in FeN4 Center Embedded in Graphene

“…Exact numerical methods are used to account for the many-body physics introduced by the central atom, which we model as a multi-orbital Anderson-like impurity. Generalized Anderson impurity models have been applied previously to porphyrin-like molecules [32,34,37,38,74,75] to predict potential energy surfaces and electronic coupling factors [63,76] for various transition-metal complexes. The advantages of our model Hamiltonian approach are that in this way, we can account for the many-body correlation effects in a numerically exact way, and also, the computations can be scaled relatively easily to handle systems with multiple impurities and more complex geometries.…”

“…As a result of their versatility, these complexes have found a range of exciting applications in spintronics [5][6][7][8][9][10][11][12][13][14], optoelectronics [15,16], solar cells [17][18][19][20][21][22], and as building blocks of magnetic materials [23][24][25][26][27][28][29] or highly tunable qubits for quantum computing applications [30]. These complexes display important correlation physics, such as spin and orbital variants of the Kondo effect in phthalocyanine (FePc) molecules deposited on the (111) surface of noble metals [31][32][33][34][35][36][37][38]. Porphyrin-like centers can be embedded in graphene and carbon nanotubes for oxygen reduction catalysis [39][40][41][42][43][44][45][46][47][48].…”